Shock resistant missile silo installation



July 16, 1968 L. R. SODERBERG 3,392,629

SHOCK RESISTANT MISSILE SILO INSTALLATION Filed June 25, 1965 3 Sheets-Sheet 1 I'.L 1 INVENTOR LAURENCE R. SODERBERG BIJMMZ. flw

ATTORNEYS.

July 16, 1968 R. SODERBERG 3,392,629

SHOCK RESISTANT MISSILE SILO INSTALLATION Filed June 25, 1965 3 Sheets-Sheet 2 V am I NVE N TOR LAURENCE R. SODERBERG id/W mlgw ATTORNEYS y 16, 1968 1.. R. SODERBERG 3,392,629

I SHOCK RESISTANT MISSILE SILO INSTALLATION Filed June 25, 1965 3 Sheets-Sheet 3 a ".1 I S 20 3 IN VE NTOR -5 LAURENCE R. SODERBERG ATTORNEXS United States Patent 3,392,629 SHOCK RESISTANT MISSILE SILO INSTALLATION Laurence R. Soderberg, Broomfield, Colo., assignor to Martin-Marietta Corporation, New York, N.Y., a corporation of Maryland Filed June 25, 1965, Ser. No. 466,987 22 Claims. (Cl. 891.816)

This invention lies in the field of protection of persons and property against high intensity shock waves, and is directed more particularly to novel structures which tend to yield to shock waves without failure and to reduce the intensity of transmitted shock forces. While it is intended primarily for the protection of mounted ballistic missiles against nuclear attack, it has great utility in other fields such as bomb shelters for civilians and military personnel beneath the surface of land or water, and underground structures for personnel and control centers or missile storage which are well protected against bombardment or earthquake forces.

Fixed, land based missile silos have many advantages but their greatest disadvantage is immobility. There is no practical design which will survive a direct hit. Thus the continuing increase in accuracy of offensive ICBMs makes the probability of at least near misses greater and greater, requiring larger, harder, and more expensive silo installations. Even these are rapidly becoming obsolete as means to provide survivability for missiles against attack. If fixed, undefended land basing is to survive as an element of new strategic systems, it is essential to develop new silo installations which will have much greater resistance to destruction and yet will be producible at relatively low cost. The present invention satisfies these requirements.

Nuclear attack against underground missile silos can result in destruction or incapacitation of the silos from several types of structural failure. The severity of the structural kill mechanisms is related to overpressure. While the term overpressure is usually used in connection with atmospheric effects, in a fluid dynamic sense overpressure is the peak amplitude of transient pressures resulting from shock waves that can exist not only in the atmosphere but also in the soil or rock media. Protection against nuclear det-onations in the air, at the surface, and underground must be provided; and both direct and induced loadings must be considered.

Present practice is to employ rigid reinforced-concrete shell structures to resist compressive and shear loadings resulting from shock. Typical loadings on an underground silo that must be considered are: (1) compressive column loading of the missile silo resulting from vertically applied forces, (2) compressive collapsing loading of the silo resulting from laterally applied forces, (3) shear loading of the silo resulting from relative lateral displacements of the ground strata in which the silo is embedded, and (4) certain unsymmetrical loadings which are usually most severe at the upper portion of the silo.

The invention disclosed herein provides a silo design which is able to survive the extreme transient loadings from very high overpressures by yielding in certain modes, but without collapsing or suffering catastrophic damage to the silo or to the missile contained therein. Flexibility without sacrifice of basic structural integrity is the key to the design. The design criteria are established by limitations on displacement rather than limitations on maximum stress resistance. The novel flexible construction provides the only practical means of surviving extreme direct ground shock resulting from subsurface high yield detonations or from proximity to the crater formed by high yield, above-surface bursts.

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In one of its simplest forms, the invention is put into practice by providing a cavity in the soil, which cavity preferably is vertical, although a generally horizontal cavity in a hillside is quite suitable as a basis for a civilian bomb shelter. The shock resisting component comprises a tube or envelope of strong flexible material of substantially the same length as the cavity, together with reinforcing and mounting rings. The reinforcing, or compression, rings are of about the same diameter as the envelope and are located within it at spaced points along its length and are arranged in planes normal to the longitudinal axis of the envelope when it is extended. The mounting rings include a suspension ring connected to the upper or outer end of the envelope and a base ring connected to the lower or inner end of the envelope.

The above assembly is placed in the cavity, which has somewhat larger lateral dimensions than the envelope, the base ring being lowered to the bottom of the cavity and anchored in the earth. The suspension ring is then anchored in the earth at the outer end of the cavity. The base ring may be any type of disk-like plate or have any kind of closure, but usually an end closure is provided by an end wall of the same material as the side wall of the envelope and extending across the opening in the base ring. The space between the cavity wall and the envelope wall is now filled with any material, such as some of the excavated soil or supplementary shock mitigating material. A cover member is also provided for the open upper end of the envelope. It may be similar to any of the silo doors conventionally being used, but preferably is a hollow, flexible member directly secured to the suspension ring and containing flowable material to provide resistance to shock forces or nuclear radiation or both. Means are provided to destroy the cover and dump its contents when it is desired to launch the missile.

The backfill flows under the influence of gravity, and tamping if necessary, until it forces the flexible and elastically recoverable envelope wall radially inwardly between each pair of compression rings to form what might be called annular arches. The arching of the wall material places it in longitudinal tension as in a series of toggles, and also applies inwardly directed radial loads to each compression ring which resists the loads in hoop compression.

The flexible construction described above accommodates various types of loads in the following ways, stated very generally. When vertical forces are applied from the air, the column collapsing force causes the envelope arches mentioned above to move radially inward to some extent. When laterally applied ground forces are encountered, the compressive radi-al collapse also results in further inward movement of the arches. The toggle action tends to shorten the envelope and this is resisted by the anchorage of the suspension ring and base ring. Actually they approach each other axially to some extent and their movement is resisted and damped by the compaction of the soil.

Shear forces resulting from opposite lateral displacements of ground strata are accommodated by relative lateral movement of the various compression rings, which movement is readily permitted by the flexibility of the envelope wall. Various unsymmetrical loadings are mainly resisted by the bending strength of the rings and plastic deformation of the surrounding ground.

It will thus be seen that the present novel construction'responds to the various peak loads imposed on it by yielding and elastically recovering rather than by rigidly resisting up to the point of failure. This yielding, together with the use of suitable shock absorbing connections between the silo and the missile, greatly reduces the total shock on the missile and also reduces the possibility of relative displacement to an inoperative position or attitude. Of course it is to be understood that very close bursts will incapacitate the system by restricting the attitude or flyout path of the missile, such bursts being of a magnitude which would destroy a conventional hard silo. It is also understood and accepted that no silo construction is presently known which can survive a direct hit.

Various other advantages and features of novelty will become apparent as the description proceeds with reference to the accompanying drawings, in Which:

FIGURE 1 is a partially schematic vertical sectional view of one presently preferred form of missile silo installation incorporating the invention;

FIGURE 2 is a fragmentary sectional view of the roof member, taken on line -22 of FIGURE 1;

FIGURE 3 is a view similar to FIGURE 1 and showing the lower portion of a modified form of the-invention; and

FIGURE 4 is a schematic illustration in plan view of the missile support and shock isolation system used in the construction of FIGURE 3.

One of the presently preferred forms of the invention is illustrated in FIGURE 1, in which an elongate, vertically extending cavity is formed in the earth 12. It is preferably substantially cylindrical in cross section although other sections may be used for special purposes. The upper end of the cavity is laterally enlarged as indicated at 14 to receive various supporting members.

A missile enclosure 16 is provided to be mounted within the cavity and includes an elongate envelope 18 of somewhat smaller diameter than the cavity, a plurality of compression rings 20 within the envelope, first support means including a suspension ring 22 connected to the upper or outer end of the envelope, and second support means including base ring 24 secured to the lower or inner end of the envelope. All of the rings are preferably made of high strength steel tubing of cylindrical or oval cross section although they may be made of other structural materials such as I-beams. Rings 22 and 24 are of larger cross section and greater strength because they are on occasion subjected to assymetrical and biaxial loads.

The envelope 18 is formed of a material which is strong, flexible, and elastically recoverable. It has been found that high strength synthetic plastics such as nylon and Dacron webbing are highly suitable. Lengths of this material are woven on the bias, or in generally goedesic configuration, as indicated at 26. It is contemplated that in extremely large installations the plastic materials may be replaced by steel cables which have the necessary elasticity for the purpose. The entire surface of the envelope is covered or coated with a barrier layer 28 of nonporous material to prevent ingress of soil or moisture. Mylar and similar materials are suitable for this purpose. The upper open end of the envelope may be secured to the suspension ring 22 by any suitable means including a reinforcing ring and bolts, not shown.

A radially extensive ring truss 30 includes a seating ring 32 to receive the suspension ring 22, which may be connected by spot welding or by bolts. The ring truss in turn is mounted on an annular bearing plate 34 of concrete, which may be reinforced if necessary. The entire weight of the envelope and compression rings is supported by the suspension ring, which in turn is supported by the truss and bearing plate which are buried in the ground at the upper end of the cavity as shown. In addition, a portion of the thrust reaction of the missile at launch is transferred to ring 22 through envelope 18.

It will be seen that compression rings 20 are located at spaced points or stations vertically of the envelope and that they are so arranged that each lies in a horizontal plane normal to the longitudinal axis of the envelope. In order to position them properly during assembly and to retain them in position during the useful life of the structure, three or more elongate cables 36 are provided. Each cable is secured at its upper end, as by welding, to ring 22 and extends downwardly to ring 24 where it is similarly secured. At each vertical station a collar 38 is swaged or welded to the cable and is connected by a short tie rod 40 to its respective ring 20. The cables are substantially evenly spaced about the periphery of the rings.

The lower end of the envelope may be secured to base ring 24 by any suitable means similar to the connection of the upper end to ring 22. The base ring may actually be a circular fiat plate forming the bottom of the enclosure, but it is preferred to use a tubular ring as shown. In this case a lower or inner end wall 42 is provided of the same material as the side wall and is integrally united thereto. The barrier layer 28 also covers the end wall. Seating of base ring 24 in the bottom of the envelope with its end wall effectively secures them together.

It is, of course, essential to anchor the base ring in the bottom of the cavity. To accomplish this, a plurality of holes 44 are drilled around the periphery, angling downwardly and outwardly. A conventional mine anchor or rock bolt 46 having an expandable gripping head 48 is seated and locked in each hole by means of the tightening bolt 50. The anchor 46 has a radial flange 52 at its upper end engaged by split clamp 54 which surrounds base ring 24. Bolt 56 and other bolts not shown are tightened to lock the anchor 46 and base ring together. After the assembly is completed, concrete 58 is poured around the anchor to further secure it against dislodge ment. This arrangement resists upward thrust loads of as much as eight million pounds.

To complete a means for mounting a missile, a compression ring 60 of about the same dimensions as base ring 24 is located a short distance above it and is supported by the cables 36. As diagrammatically shown, a series of struts 62 are pivotally connected around the inner periphery of base ring 24 and a similar series of struts 64 are pivotally connected to mounting plate 66 and to struts 62. Another series of shock absorbing struts 68 are pivotally connected to ring 60 and to the connections between struts 62 and 64 to complete a shock absorbing trusswork. Mounting plate 66 receives the lower end of missile 70 and supports it in upright position spaced from the wall of envelope 18.

Since lateral disturbances of base ring 24 and mounting plate 66 tend to tilt the missile about its center of gravity, shock absorbing restraining means 72 are mounted on some of the compression rings 20 near the center of gravity and the upper end of the missile and are provided with shoes 74 to engage the wall 76 of the missile and yieldingly resist its motion relative to the envelope. They are designed in known manner to fall away when the missile is about to be launched.

The closure of the envelope is completed by a cover member 78 which is secured directly to suspension ring 22, as by reinforcing rings and bolts. It is composed of upper and lower webs or membranes 80 and 82 forming a chamber 84 between them and the suspension ring. The webs are formed of the same material 26 as the wall of the envelope and are covered by the same barrier layer 28. Chamber 84 is filled with soil or other material to resist the force of an air burst. Alternatively it may be filled with a material such as a liquid lithium hydride slurry to attenuate the radiation from a nuclear burst. As seen in FIGURE 2, the lower web may be made thicker and stronger to support the weight of the contents of chamber 84.

It is necessary to provide some means to effectively remove the cover member and its contents when the missile is to be launched. One way is illustrated in FIG- URE 2, where a liner 86 is provided on the inner face of webs 80 and 82. The liners are provided with a plurality of diametrically extending primacords 88 which may be detonated to rupture the webbing and dump the contents of the cover to the bottom of the cavity. In

the event that extremely heavy loads are to be sustained, the plastic webbing can be reinforced or replaced by woven steel cable webbing which can be releasably held by explosive bolts.

When the entire assembly is set and secured in place as shown in FIGURE 1 and described above, the backfill 90 is poured into the gap between the wall of the envelope and the wall of the cavity, and tamped if necessary. Soil is filled in all the way up to earth level as indicated in FIGURE 1, and the missile and its enclosure-are protected against the elements and against bombardment.

The initial gravity load of the backfill produces radially inward pressures on the wall of envelope 18 and causes it to assume the series of annular arch forms 92 illus trated in FIGURE 1 putting longitudinal tension in the envelope wall. The toggle or scissors effect of this force also applies radially inward force to each of the compression rings 20 and places them in hoop compression, which they are particularly well adapted to resist.

When a surface or underground burst occurs to one side of the installation a very high peak pressure wave passes through the ground and exerts a compressive force which may be in excess of 100 p.s.i. This force urges the arches 92 inwardly several inches and the force is transmitted to compression rings 20, which are designed to withstand the maximum load of this kind which will be encountered. The yielding of the webbing forming the envelope wall allows movement of the backfill which absorbs a large part of the energy, and the temporary partial collapse does not constitute a failure. After the peak load passes, the elastic recovery of the webbing returns it substantially to its original position.

The added arching of the envelope wall, through toggle action, produces a column shortening force which may be as high as eight million pounds, tending to pull rings 22 and 24 toward each other. Anchors 46 restrain ring '24 against upward movement, and truss and bearing plate 34 resist downward movement of suspension ring 22. To the extent that the upper mounting moves downward it produces compressive plastic deformation of the soil which acts as a damped spring and absorbs a substantial amount of energy.

The burst force may be so directed or the ground strata may be so formed that opposite lateral forces are exerted on upper and lower portions of the enclosure. In this case any of the rings 20, 22, 24 can move rela tively laterally through a considerable distance without rupturing the webbing of the envelope wall. Sometimes the ground will return to its original position after passage of the shock force and the enclosure will again be in alignment. Even if it does not, the missile can still be launched unless the distortion is so great as to reduce the flyout clearance to little more than zero.

In the event of an overhead air burst, the downward force is applied to cover member 78 and is transmitted to suspension ring 22. The result is a vertical column collapse to the extent permitted by bearing plate 34. Since the enclosure can yield most readily in this mode, a very high force can be accommodated without damage.

It will be apparent that the construction described will offer the same protection to personnel or equipment located within the same type of enclosure. Similar struc tures may be used as civilian bomb shelters and may be built into horizontal or sloping cavities in hillsides. They may have generally rectangular cross sections for greater utility although the cylindrical cross section gives a greater strength weight ratio. The structure is also highly suitable for protection of delicate instruments and the like against earthquake shocks which produce some of the same types of forces.

In the event that there is no suitable rock stratum available for anchorage of the bottom of the enclosure, a modified construction as shown in FIGURE 3 can be employed. The total structure is substantially identical to that of FIGURE 1 but the rock bolt anchorage is replaced by truss 30 inverted to resist upward forces on base ring 24 and a concrete bearing plate 94 which is substantially the same as bearing plate 34 inverted. The axial shortening caused by either an air burst or lateral ground compression will be resisted by compressive plastic deformation of the soil axially located between bearing plates 34 and 94. To further increase energy absorption the backfill, or even all of the soil between the bearing plates, can be replaced by supplementary shock mitigating material such as crushable granular vermiculite. Instead of using a series of cables as in FIGURE 1, compression rings 20 may be supported in place by webbing or metal saddles 96 individually secured to the envelope wall.

A modified missile support and shock isolation system is shown in FIGURE 3 and diagrammatically illustrated in FIGURE 4. The mounting plate 66 is carried by a truss-like arrangement of shock absorbing struts 98 pivotally connected :at their upper ends to plate 66 and at their-lower ends to load pads 100 which in turn are welded or otherwise secured at spaced points about the periphery of base ring 24. Mounting plate 66 supports missile 70 in cantilever fashion in the same way as in FIGURE 1. The shock absorbing restrainers 72 also contact the missile to preclude undesirable tilting in the same way as in FIGURE 1. Any or all of the various shock absorbing struts in the structure may be of the variable orifice type and may be acceleration controlled, as are many shock struts in modern automobiles.

Flexibility is the key to the fundamental difference between the silo installation of this invention and the conventional hard type. The flexible enclosure takes advantage of the fact that the loads are transient even though the intensity is high, and it rolls with the punch and recovers completely or substantially to its original position and condition after the shock wave has passed. To survive a comparable force, a hardened silo would have to be built much larger and heavier than the present day hardened silos, and would be much more expensive than either the old hard type or the new flexible type.

The hardened or rigid silo, by its very nature, resists and withstands the full force of a shock wave up to its ultimate strength, at which point failure tends to be complete and abrupt, after which the full force of the shock wave is transmitted to the missile and disables it.

On the contrary, the initial yielding of the flexible silo enclosure of this invention, together with the movement and plastic deformation of the backfill, absorbs much of the energy of the shock wave and reduces its peak intensity effect on the structure. This, in effect, reduces the load which the structure must withstand. Even when the deformation of the flexible enclosure goes beyond the point of full elastic recoverability, the continuing deformation constitutes a gradual and partial failure with much less shock to the missile. In fact it is contemplated that even when failure is substantial enough to impair flyout clearance or missile system alignment, the shock to the missile may be so slight as to cause no serious damage and it may be removed and launched from a usable silo.

It will be apparent to those skilled in the art that various changes and modifications may be made in the construction and arrangement of parts as disclosed without departing from the spirit of the invention, and it is intended that all such changes and modifications shall be embraced within the scope of the followings claims.

I claim:

1. A shock resistant missile silo installation comprising: an elongate, vertically extending cavity in the earth and a missile enclosure secured therein; said enclosure including an elongate, generally cylindrical envelope having a wall of strong flexible material extending throughout the major portion of the vertical length of said cavity, and a plurality of horizontally arranged, annular compression rings within and spaced along the length of the wall of said envelope to reinforce it against radial collapse; a suspension ring at the upper end of said cavity connected to the upper end of said envelope and mounted on a bearing member to support said envelope; a base member at the lower end of said cavity secured to the lower end of said envelope and anchored in the earth to resist upward movement of said envelope; means within said enclosure to support a missile in vertical attitude spaced from the wall of said envelope; and cover means to close the open upper end of said enclosure.

2. A shock resist-ant missile silo installation comprising: an elongate, vertically extending cavity in the earth and a missile enclosure secured therein; said enclosure including an elongate, generally cylindrical envelope having a wall of strong flexible material extending throughout the major portion of the vertical length of said cavity and being subject to radial collapse in response to radially inwardly directed shock forces resulting from bombardment, and a plurality of horizontally arranged annular compression rings within and spaced along the length of said envelope and engaging the wall of said envelope to reinforce it against radial collapse; support means mounted at the upper end of said cavity and provided with an opening of substantially the same size as the cross section of said envelope, and connected to the upper end of said envelope to support it in said cavity; a base ring at the lower end of said cavity secured to the lower end of said envelope and anchored in the earth to resist upward movement of said envelope; and means within said enclosure to support a missile in vertical attitude spaced from the wall of said envelope.

3. A shock resistant subterranean structure adapted to house humans or articles and protect them from high intensity shock forces, comprising: an elongate cavity extending into the earth and an enclosure secured therein; said enclosure including an elongate envelope having a wall of strong flexible material extending throughout the major portion of the length of said cavity, and a plurality of compression rings within said envelope and en gaging said wall to reinforce it against radial collapse; said rings being spaced along the length of said envelope and being arranged in planes normal to the longitudinal axis of said envelope; :first support means anchored at the outer end of said cavity and connected to the outer end of the envelope; and second support means anchored at the inner end of said cavity and connected to the inner end of said envelope; the application of inwardly directed ground shock forces to said envelope causing said wall to collapse inwardly and form arches between said compression rings, applying generally radial loads thereto to be resisted thereby; the forming of said arches also tending to shorten the axial length of said envelope; and the anchorage of said first and second support means resisting the shortening tendency.

4. A structure as claimed in claim 3; said wall comprising woven fabric of lengths of elastically recoverable material.

5. A structure as claimed in claim 4; said envelope having an inner end wall of the same material.

6. A structure as claimed in claim 5; said walls being covered with a barrier layer of non-porous material to prevent the ingress of soil and moisture.

7. A shock resistant missile silo installation comprising: an elongate, vertically extending cavity in the earth and a missile enclosure secured therein; said enclosure including an elongate, generally cylindrical envelope having a wall of strong flexible material extending throughout the major portion of the length of said cavity and being subject to radial collapse in response to radially inwardly directed ground shock forces, and a plurality of annular compression rings within said envelope and engaging said wall to reinforce it against radial collapse; said rings being spaced along the length of said envelope and being arranged in planes normal to the longitudinal axis of said envelope; a suspension ring of substantially the same diameter as said envelope anchored at the upper end of said cavity and connected to the upper end of said envelope to support it in said cavity; a base ring of substantially the same diameter as said envelope connected to the lower end of said envelope and anchored in the earth at the bottom of said cavity to resist upward movement of said envelope; and means within said enclosure to support a missile.

8. A construction as claimed in claim 7; said wall comprising a fabric woven of lengths of elastically recoverable material.

9. A construction as claimed in claim 8; said envelope having a lower end wall of the same material.

10. A construction as claimed in claim 9; said walls being covered with a barrier layer of non-porousmaterial to prevent the ingress of soil and moisture.

11. A construction as claimed in claim 7; and ,a cover member carried by said suspension ring.

12. A construction as claimed in claim 11; said cover member including material serving to resist the overpressure of air bursts.

13. A construction as claimed in claim 11; said cover member including material serving to attenuate the radiation resulting from nuclear bursts.

14. A construction as claimed in claim 7; said means to support a missile comprising a horizontal mounting plate adapted to engage the lower end of the missile and shock absorbing means connecting said mounting of plate to said base ring.

15. A construction as claimed in claim 14; and shock absorbing restraining means mounted on at least one compression ring and adapted to engage the wall of a missile to assist in maintaining its upright attitude.

16. A construction as claimed in claim 7; and a mass of granular material surrounding said envelope between the wall of said envelope and the wall of said cavity and adapted to yield and absorb a part of the force exerted by a ground shock wave.

17. A construction as claimed in claim 7; said compression rings being secured to the wall of said envelope.

18. A construction as claimed in claim 7; and a plurality of suspension cables secured to said suspension ring and extending downwardly throughout the major portion of the length of said envelope; said compression rings being secured to spaced points along the lengths of said cables to be supported thereby.

19. A shock resistant missile silo installation comprising: an elongate, vertically extending cavity in the earth and a missile enclosure secured therein; said enclosure including an elongate, generally cylindrical envelope having a wall of strong flexible material extending throughout the major portion of the length of said cavity and being subject to radial collapse in response to radially inwardly directed ground shock forces, and a plurality of annular compression rings within said envelope and engaging said wall to reinforce it against radial collapse; said rings being spaced along the length of said envelope and being arranged in planes normal to the longitudinal axis of said envelope; a suspension ring at the upper end of said cavity; a first annular bearing plate at the upper end of said cavity surrounding said envelope and extending radially outwardly therefrom and anchored in the earth; said suspension ring being secured to said first bearing plate and connected to and supporting said envelope; a base ring at the lower end of said cavity; a second annular bearing plate at the lower end of said cavity surrounding said envelope and extending radially outward therefrom and anchored in the earth; said base ring being secured to said second bearing plate and connected to the lower end of said envelope; the application of inwardly directed ground shock forces to said envelope causing said wall to collapse radially inwardly and form arches between said compression rings, applying generally radial 9 loads thereto to be resisted thereby; the forming of said arches also tending to shorten the axial length of said envelope and urge the opposing bearing plates toward each other; the axial approach of said bearing plates compacting the soil between them to produce a damped spring action opposing vertical and radial collapse.

20. A construction as claimed in claim 19; at least a part of the soil located between said bearing plates being a crushable granular material capable of absorbing a substantial amount of energy in failure.

21. A flexible yieldable missile silo component for use in producing a shock resistant missile silo installation, comprising: an elongate, generally cylindrical envelope having a side wall and one end wall of strong flexible material adapted to collapse readily under external pressures; a plurality of annular compression rings within said envelope and secured to said side wall at spaced points along its length; each compression ring being so secured to said side wall that when the envelope is extended each compression ring will lie in a plane normal to the longitudinal axis of the envelope to support the side wall against radial collapse; a base ring secured to said envelope adjacent said end wall; and a suspension ring secured to said envelope adjacent its opposite end; said suspension ring being adapted to be anchored in the earth at the upper end of a cavity formed to receive the envelope; and said base ring being adapted to be anchored in the earth at the lower end of said cavity.

22. A component as claimed in claim 21; and a cover member adapted to be secured to said suspension ring.

References Cited UNITED STATES PATENTS 3,072,022 1/1963 Wood et al. 89-1.818 X 3,158,062 11/1964 Feiler 89--1.817 X 3,160,060 12/1964 Zsoka et al. 891.816

SAMUEL W. ENGLE, Primary Examiner. 

1. A SHOCK RESISTANT MISSILE SILO INSTALLATION COMPRISING: AN ELONGATE, VERTICALLY EXTENDING CAVITY IN THE EARTH AND A MISSILE ENCLOSURE SECURED THEREIN; SAID ENCLOSURE INCLUDING AN ELONGATE, GENERALLY CYLINDRICAL ENVELOPE HAVING A WALL OF STRONG FLEXIBLE MATERIAL EXTENDING THROUGHOUT THE MAJOR PORTION OF THE VERTICAL LENGTH OF SAID CAVITY, AND A PLURALITY OF HORIZONTALLY ARRANGED, ANNULAR COMPRESSION RINGS WITHIN AND SPACED ALONG THE LENGTH OF THE WALL OF SAID ENVELOPE TO REINFORCE IT AGAINST RADIAL COLLAPSE; A SUSPENSION RING AT THE UPPER END OF SAID CAVITY CONNECTED TO THE UPPER END OF SAID ENVELOPE AND MOUNTED ON A BEARING MEMBER TO SUPPORT SAID ENVELOPE; A BASE MEMBER AT THE LOWER END OF SAID CAVITY SECURED TO THE LOWER END OF SAID ENVELOPE AND ANCHORED IN THE EARTH TO RESIST UPWARD MOVEMENT OF SAID ENVELOPE; MEANS WITHIN SAID ENCLOSURE TO SUPPORT A MISSILE IN VERTICAL ATTITUDE SPACED FROM THE WALL OF SAID ENVELOPE; AND COVER MEANS TO CLOSE THE OPEN UPPER END OF SAID ENCLOSURE. 